As is known, in motorcycles, the front wheels often comprise two brake discs which are mounted symmetrically on opposite sides of a central plane of the wheel and astride which associated disc-brake calipers are mounted. The radial dimensions of each brake-disc and brake-caliper assembly constitute an obstacle which hinders access to the tire-inflation valve which projects radially from the rim towards the hub of the wheel.
Access to the valve is also difficult in the rear wheels since, on one side of the wheel, there is usually the transmission unit comprising a chain wheel coaxial with the wheel and a chain associated therewith, together with a casing system and, on the other side, there is the brake disc; moreover, on both sides, there are the side members of the fork which supports the rear wheel.
The tire-inflation operation is therefore slow and complex and often forces the operator to use both hands. In fact it is necessary to grip the air-supply hose with one hand and to hold the pressure-gauge nozzle in position on the inflation valve with the other hand because the air-supply hose has to extend around a right angle so that the nozzle tends to become misaligned relative to the valve, causing leakages of fluid.
These problems are further aggravated in high-performance motorcycles having large-diameter brake discs which form a veritable labyrinth for access to the valve.
To overcome these problems, it is known to provide a wheel comprising two annular ducts, one in the region of the wheel hub and the other in the region of the periphery of the wheel, the annular ducts being in fluid communication with one another by means of at least one internally hollow spoke.
An example of this solution is disclosed in U.S. Pat. No. 5,641,208. However, this solution requires complex and expensive processes for the manufacture of the spokes and limits the possibilities for the implementation of complex geometries for the spokes.
Moreover, a solution of this type is impracticable for motorcycle wheels because the wheels would be positioned asymmetrically with respect to a plane of symmetry of the front wheel-and-axle set, which would be dynamically unbalanced; furthermore, the arrangement of the brakes would be extremely difficult.
The object of the present invention is to provide a wheel for vehicles which solves the problems mentioned with reference to the prior art.